This application is submitted in response to the Challenge Grant Program, specifically the Regeneration challenge area, program 11-HL 101, "Develop cell based therapies for CV, lung and blood disease". The proposal fulfills all the expectations of the ARAA of 2009: 1) It will create two new jobs to the American citizens, 2) It proposes to investigate a novel and innovated hypothesis for the treatment of pulmonary hypertension (PH), a devastating disease without a cure and 3) it will allow us to fast-track our studies to a phase 1 clinical trial with the potential of saving thousands of American lives and reducing disease associated morbidity in the immediate future. The progression of the fatal disease PH is set in motion by pulmonary vascular endothelial dysfunction. As a result of this concept, vasodilatory therapy has been the mainstay of PH treatment however, despite some success, PH remains a deadly disease. We believe this proposal described a conceptual breakthrough that is urgently needed to develop the novel therapeutics that will prevent and even cure PH. Angiotensin converting enzyme 2 (ACE2) is the key enzyme of the renin-angiotensin system present in endothelial cells. ACE2 produces angiotensin-(1-7) [Ang-(1-7)] which prevents the vasoconstrictive, proliferative, fibrotic and inflammatory effects of Ang II, a product of angiotensin converting enzyme (ACE). We hypothesize that an imbalance in the ACE/ACE2 ratio is the key event in pulmonary endothelial dysfunction leading to the vascular remodeling and the pathophysiology associated with PH. This hypothesis has been supported by our data demonstrating that overexpression of pulmonary ACE2 by lung gene transfer prevents and even reverses PH in animal models. This novel concept, however, has one difficulty to overcome before its preclinical trial. This relates to a limited success associated with viral vector mediated gene transfer to the lung. To overcome this obstacle, we propose to utilize hematopoietic stem cells (HSC) that differentiate into endothelial precursor cells (EPC), expressing ACE2 or Ang-(1-7) to deliver ACE2/Ang-(1-7) to sites of injury to orchestrate robust pulmonary vascular repair and reverse PH. We propose three specific aims to accomplish this objective: Aim 1: Test that overexpression of ACE2 by HSC in the lungs will reverse PH pathophysiology in the monocrotaline (MCT) rat model of PH. Aim 2: Test the hypothesis that delivery of HSC expressing ACE2 or Ang-(1-7) would reverse PH in the hypoxia rat model and the conditional knock-in of bone morphogenetic protein receptor 2 (Bmpr2) mouse model. Aim 3: We will investigate the hypothesis that ACE2/Ang-(1-7)-HSC will be protective by enhancing endothelial function, reducing smooth muscle cell hyperplasia and decreasing proinflammatory cytokines. These studies will position us to translate our investigation into a phase 1 clinical study for the use of ACE2/Ang-(1-7) engineered autologous EPC for the treatment of PH. This application is in response to Challenge Grant Program # 11HL-101 in the area of "Develop cell based therapies for CV, lung, and blood disease". Current therapy for pulmonary hypertension (PH) is not effective and as a result PH remains a fatal disease. Our objective in this investigation is to use genetically modified hematopoietic stem cells to deliver ACE2 or Ang-(1-7) to the site of pulmonary injury to orchestrate a robust pulmonary vascular repair and reverse PH. PUBLIC HEALTH RELEVANCE: This application is in response to Challenge Grant Program # 11HL-101 in the area of "Develop cell based therapies for CV, lung, and blood disease". Current therapy for pulmonary hypertension (PH) is not effective and as a result PH remains a fatal disease. Our objective in this investigation is to use genetically modified hematopoietic stem cells to deliver ACE2 or Ang-(1-7) to the site of pulmonary injury to orchestrate a robust pulmonary vascular repair and reverse PH.